Wire, Wire, More Wire

[JOHNMAN]

I have a question for any pros out there that don't mind answering a question or two for me.

I am currently wiring my new shop. It's a 40' X 64' building (pole barn).

I am running 20A 120V circuits for outlets along the opposite wall (64' away). If I count going up the wall and down the opposite wall, my furthest outlet is about 100ft away.

The wire size calculator that I am using is calling out #8 wire.

#8 wire seems big, especially when terminating to an outlet even in a deep box. It's probably too late for me on this project, but I would still like to know what others have done when running a 20A 120V circuit over a long distance.

The original wire to the outlets the previous owner had was #12. My wire size calculator also calls out #8 if it was only 15A as well, but says that I could go to 153' #8 at 15A.

Another question I have is wire for lighting. I want to put in some 3-way switches for my overhead lighting. How would I measure the distance? From breaker to the light switches then to the lights????

Any opinions?

 

[LoneGunman]

I know of no electrical contractor that uses anything larger than #12 copper for a 100' 20 amp circuit, we don't and I have never worked for one that did.

Your second question would depend on how you ran your 3 ways BUT in a 60' x 40' building I would not run anything larger than 12 for any 20 amp circuit.

 

[tfi racing]

I agree,there is something fishy about the calculator you are using.#12 should be more than adequate,I wouldn't hesitate in using it for your receptacles or your 3 way switch travellers.

 

[Kevin54]

# 12 wire should be adequate with no voltage drop. Once the power is turned on it will fill the wire full of electricity as long as you have an outlet so you don't deadhead the electricity. Running multiple tools at one time might drain the electricity from the wire but as long as the box is pushing it hard enough it should stay full.



Seriously though........I helped an electrician wire my nephews 50x100 pole building and we used #12 everywhere with no problems.

 

[walrus]

The wire size calculator that I am using is calling out #8 wire.

#8 wire seems big, especially when terminating to an outlet even in a deep box. It's probably too late for me on this project, but I would still like to know what others have done when running a 20A 120V circuit over a long distance.

The original wire to the outlets the previous owner had was #12. My wire size calculator also calls out #8 if it was only 15A as well, but says that I could go to 153' #8 at 15A.

Another question I have is wire for lighting. I want to put in some 3-way switches for my overhead lighting. How would I measure the distance? From breaker to the light switches then to the lights????

Any opinions?

Whats the real load you are trying to run. Those calculators use the real load not the breaker size.

 

[JOHNMAN]

Why would I not size the wire for the breaker capacity?

As I look at a few more of the "calculators", I come to the realization that it depends upon voltage drop as well. If voltage drop is not a concern, I could use 12GA wire.

I do know that as voltage drops, the current draw of the load increases.

I also now know that I should have very little voltage drop even at the outlets furthest from the breaker.

I also now know that I need not run big huge wire for lighting. (I don't believe that the florescent balasts will draw much current and I don't think they will be effected with a bit of voltage drop.

I did find a more detailed calculator that cleared some of this up for me.

Thanks for your comments (they did inspire me to find out how most "get away with" using 12GA wire).

 

[walrus]

Why would I not size the wire for the breaker capacity?
).

Because the breaker capacity isn't the load. You can't load a 20 amp breaker with 20 amps of lighting load or at least you can't legally